Cellular systems typically comprise a plurality of cells and allow mobiles such as mobile telephones or user equipment, UE, to roam between the cells. Communications in a cell may take place between mobile units and a base station, BS, of the cell. When designing cellular networks, cells may be provisioned with lists of neighbouring cells. Such lists are called neighbour lists and may contain, for example, a list of scrambling codes of adjacent cells. Scrambling codes are used in code division multiple access, CDMA, based cellular networks. In systems or cells using time division multiple access, TDMA, technology, neighbour lists may comprise information on frequencies in use in neighbouring cells.
An UE camping in a cell may be configured to receive the neighbour list and subsequently search for signals using the scrambling codes contained therein. When certain trigger criteria are met, the UE and network may be configured to co-operatively transfer the UE to one of the neighbouring cells. Trigger criteria may include the UE measuring a certain amount of energy on one of the scrambling codes in the neighbour list while experiencing a weak signal from the cell it is camped in, which may correspond to the UE being located near a cell edge geographically. The transferring of the UE may be known as a handover procedure, a cell selection procedure or a cell reselection procedure, for example. A UE is transferred from a source cell to a target cell, wherein the UE is attached to the source cell before the handover or reselection procedure and the UE is attached to the target cell after the handover or reselection procedure.
Sometimes it may be straightforward to define neighbour lists for certain cells, but it may occur that the process is less straightforward depending on e.g. radio propagation characteristics. Compiling the neighbour list for each cell in a cellular network may entail a significant effort in the network planning stage. Networks that are designed to at least in part automate the compilation of neighbour lists may be known as self-organizing networks, SON.